1. Field of the Invention
The present invention relates in general to a fluid-filled cylindrical elastic mount suitably used for flexibly mounting a member of a suspension system of an automotive vehicle on a body of the vehicle, for example, and more particularly to such a fluid-filled cylindrical elastic mount which is capable of effectively damping input vibrations applied in the axial direction of the mount, based on flow of the fluid contained in the mount.
2. Discussion of the Related Art
As one type of a mounting device interposed between two members in a vibration system to connect these two members in a vibration-damping fashion, there is known a cylindrical elastic mount wherein an inner and an outer sleeve are disposed in a radially spaced relationship and are elastically connected by an elastic body interposed therebetween, primarily for damping or isolating vibrations applied between the two sleeves in their axial direction. Such a cylindrical elastic mount is suitably used in automotive suspension systems, for example, as a suspension member mount, a strut-bar cushion, and an upper support.
To meet with an increasing requirement for a cylindrical elastic mount having an improved vibration damping or isolating function, there is recently proposed a fluid-filled cylindrical elastic mount having a chamber which is filled with a fluid and consists of a plurality of sections that are held in fluid communication with each other through a restricted fluid passage or passages. The fluid-filled elastic mount of this type is capable of damping vibrations based on flow of the fluid between the fluid chamber sections through the restricted fluid passage(s).
The assignee of this application proposed one example of the above type of fluid-filled cylindrical elastic mount, as disclosed in laid-open Publication No. 3-12641 of unexamined Japanese Utility Model Application. The proposed elastic mount has a groove-like pocket which is formed in an elastic body connecting inner and outer sleeves, such that the pocket extends over the entire circumference thereof. With this annular pocket closed by the outer sleeve, there is formed an annular fluid chamber, which is divided by an annular partition member into axially opposed two sections. The partition member, which is constituted by a plurality of arcuate or semi-circular blocks, is disposed in the pocket of the elastic body, and is kept in place with its outer circumferential surface supported by the outer sleeve. At the same time, an annular restricted fluid passage is formed between the inner circumferential surface of the partition member and the bottom wall surface of the pocket, such that the restricted fluid passage communicates with the two sections of the fluid chamber.
In the thus constructed fluid-filled cylindrical elastic mount, the annular restricted fluid passage is provided in a radially inner portion of the annular fluid chamber. This means that the restricted fluid passage has a comparatively small circumferential length. Accordingly, the cross sectional area of the restricted fluid passage which permits flow of the fluid therethrough can be sufficiently reduced, without excessively limiting the amount of relative displacement of the inner and outer sleeves in their radial directions. Consequently, the elastic mount provides a sufficiently high damping effect with respect to input vibrations having relatively low frequencies, based on the resonance of the fluid in the restricted fluid passage.
The above-described fluid-filled cylindrical elastic mount is also advantageous in that the axially opposed fluid chamber sections connected by the restricted fluid passage may be easily formed with high efficiency, by inserting the separate blocks of the partition member from the exterior into the pocket, and then fitting the outer sleeve on the partition member and an inner assembly including the elastic body and inner sleeve.
However, further studies by the inventors of the present invention revealed that the fluid-filled cylindrical elastic mount as proposed still has a room for improvements in its structure. Namely, the partition member used in this elastic mount consists of the arcuate or semi-circular blocks, in other words, circumferentially divided blocks, which are separately put into the pocket and assembled together at a radially outer portion of the pocket. During this assembling procedure, it is difficult to maintain the annular shape formed by the blocks thus assembled. This also makes it difficult to fit the outer sleeve onto the outer surface of the partition member while maintaining the annular shape of the partition member formed by the blocks.
Thus, the proposed cylindrical elastic mount is produced with a considerably low efficiency, due to the problem as described above. The production efficiency is also lowered by the above-described process step in which the fitting of the outer sleeve on the inner assembly is effected within a mass of the fluid.